Claims:

2. The nanocomposite of claim 1, wherein the polyolefin comprises
homopolymers, copolymers, blends of polymers, mixtures of polymers,
alloys of polymers, or combinations thereof,wherein at least one of the
polymers is polymerized from an olefin monomer having from 2 to about 8
carbon atoms.

4. The nanocomposite of claim 1, wherein the organoclay is a
montmorillonite clay intercalated with an organic or semi-organic
chemical capable of entering the montmorillonite clay gallery and bonding
to the surface.

5. The nanocomposite of claim 1, wherein the compatibilizer is a maleated
polypropylene.

6. The nanocomposite of claim 1, wherein the metal scavenger is selected
from the group consisting of propionates; hydrazines; phosphites; EDTAs;
lignosulfonates; stearoyl lactylates; pyridine; methacrylates; and
combinations thereof.

18. The article of claim 12, wherein the organoclay is a montmorillonite
clay intercalated with an organic or semi-organic chemical capable of
entering the montmorillonite clay gallery and bonding to the surface and
wherein the compatibilizer is a maleated polypropylene.

19. The article of claim 12, wherein the metal scavenger is selected from
the group consisting of propionates; hydrazines; phosphites; EDTAs;
lignosulfonates; stearoyl lactylates; pyridine; methacrylates; and
combinations thereof.

Description:

CLAIM OF PRIORITY

[0001]This application claims priority from U.S. Provisional Patent
Application Ser. No. 60/746,272 bearing Attorney Docket Number 12006005
and filed on May 3, 2006, which is incorporated by reference.

FIELD OF THE INVENTION

[0002]This invention concerns composites of polyolefins and organoclay
that are stable notwithstanding exposure to long term heat.

BACKGROUND OF THE INVENTION

[0003]The mixture of organoclays and polyolefins, commonly called
polyolefin nanocomposites, is highly desired because organoclays can add
stiffness and toughness to polyolefin-containing compounds. Polyolefins
for plastic structures have been useful since the mid-20th Century.
Organoclays, smectite inorganic clays intercalated with organic ions,
such as quaternary ammonium, have become useful in the last decade.

[0005]Quite unexpectedly, it has been found that the use of metal
scavengers improves the heat stability of polyolefin nanocomposites by at
least about 14% when compared polyolefin nanocomposites containing only
conventional antioxidants and phosphite stabilizers.

[0006]Thus, one aspect of this invention is a heat stabilized polyolefin
nanocomposite that comprises (a) polyolefin, (b) organoclay, (e)
compatibilizer, and (d) metal scavengers that stabilize the nanocomposite
against heat.

[0007]Another aspect of the invention are articles made from the
stabilized polyolefin nanocomposite.

[0008]Features and advantages of the invention will be explained below
while discussing the embodiments.

EMBODIMENTS OF THE INVENTION

[0009]Polyolefin

[0010]"Polyolefin" includes homopolymers, copolymers, blends of polymers,
mixtures of polymers, alloys of polymers, and combinations thereof, where
at least one of the polymers is polymerized from an olefin monomer having
from 2 to about 8 carbon atoms.

[0013]Organoclay is obtained from inorganic clay usually from the smectite
family. Smectites have a unique morphology, featuring one dimension in
the nanometer range. Montmorillonite clay is the most common member of
the smectite clay family. The montmorillonite clay particle is often
called a platelet, meaning a sheet-like structure where the dimensions in
two directions far exceed the particle's thickness.

[0014]Inorganic clay becomes commercially significant if intercalated with
an organic intercalant to become an organoclay. An intercalate is a
clay-chemical complex wherein the clay gallery spacing has increased, due
to the process of surface modification by an intercalant. Under the
proper conditions of temperature and shear, an intercalate is capable of
exfoliating in a resin polyolefin matrix. An intercalant is an organic or
semi-organic chemical capable of entering the montmorillonite clay
gallery and bonding to the surface. Exfoliation describes a dispersion of
an organoclay (surface treated inorganic clay) in a plastic matrix. In
this invention, organoclay is exfoliated at least to some extent.

[0015]In exfoliated form, inorganic clay platelets have a flexible
sheet-type structure which is remarkable for its very small size,
especially the thickness of the sheet. The length and breadth of the
particles range from 1.5 μm down to a few tenths of a micrometer.
However, the thickness is astoundingly small, measuring only about a
nanometer (a billionth of a meter). These dimensions result in extremely
high average aspect ratios (200-500). Moreover, the miniscule size and
thickness mean that a single gram contains over a million individual
particles.

[0016]Polyolefin Nanocomposites

[0017]Nanocomposites are the combination of the organoclay and the plastic
matrix. In polymer compounding, a nanocomposite is a very convenient
means of delivery of the organoclay into the ultimate compound, provided
that the plastic matrix is compatible with the principal polymer resin
components of the compounds. In such manner, nanocomposites are available
in concentrates, masterbatches, and compounds from Nanocor, Inc. of
Arlington Heights, Ill. (www.nanocor.com) and PolyOne Corporation of Avon
Lake, Ohio (www.polyone.com) in a variety of nanocomposites. Particularly
preferred organoclays are I24TL, I30P, I44P, and I44W from Nanocor, Inc.
PolyOne markets Nanoblend® brand nanoconcentrates, such as
Nanoblend® 1001 and 2201 brand concentrates.

[0018]Nanocomposites offer flame-retardancy properties because such
nanocomposite formulations burn at a noticeably reduced burning rate and
a hard char forms on the surface. They also exhibit minimum dripping and
fire sparkling.

[0019]Compatibilizer

[0020]Nanocomposites benefit from the addition of compatibilizers known to
those skilled in the art to assist in the dispersion of organoclay into
the thermoplastic matrix. In a preferred embodiment, the compatibilizer
is a grafted maleic anhydride, such as disclosed in U.S. Pat. No.
5,717,500 (Karande et al.). The use of compatibilizer is also disclosed
in U.S. Pat. No. 6,632,868 (Qian et al.). Both of these patents are
incorporated by reference herein for their teaching of the use of
compatibilizers to disperse organoclays into the thermoplastic resin.

[0021]Particularly preferred is a blend of a polyolefin with a maleated
polypropylene to serve as a compatibilizer. The maleated polypropylene is
capable of increasing dispersion of organoclay into the polyolefin,
commercially available from Chemtura Corporation under the Polybond
brand.

[0022]Metal Scavengers

[0023]"Metal scavenger" as used in this invention means a metal
deactivator or chelator which provides ligands to metal impurities, or
minimizes oxidative degradation.

[0024]The metal scavenger for the present invention are selected from the
group consisting of propionates, such as 2,2'-oxalyldiamidobis[ethyl
3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate; hydrazines, such as
1,2-bis(3,5-di-t-butyl-4-hydroxyhydrocinnamoyl)hydrazine; phosphites,
such as tris(nonylphenyl)phosphite, phenol, 4,4'-thiobis
2-(1,1-dimethylethyl) phosphite, tristearyl phosphite, tris neodol-25
phosphite, and 4,4' isopropylidenediphenol alkyl phosphites; EDTAs, such
as disodium EDTA, sodium ferric EDTA, tetraammonium EDTA,
tetrahydroxylpropyl ethylenediamine; tetrasodium EDTA, and trisodium
EDTA; lignosulfonates, such as sodium lignosulfonate; stearoyl
lactylates, such as calcium stearoyl lactylate and sodium stearoyl
lactylates; pyridine; and methacrylates such as dimethylaminoethyl
methacrylate.

[0025]Optional UV Stabilizers

[0026]UV stabilizers can be additives to the nanocomposite according to
the present invention. The UV stabilizers can be conventional to protect
the polymer resin(s) or those described especially here or both. The
special UV stabilizers protect at wavelengths influenced by the presence
of the organoclay in the nanocomposite.

[0027]The presence of organoclays in the compound can require UV
stabilizers which have good absorption above 320 nm. Therefore, any
commercially available UV stabilizer which filters light above 320 nm is
suitable as an optional ingredient for use in the present invention.

[0028]Preferably, two UVA materials can be used. Lowilite 36 brand
stabilizer, and Lowilite 234 brand stabilizer, all with good absorption
above 320 nm wavelength, were used in experimentation associated with
this invention.

[0029]Company descriptions of these UV additives are as follows:
http://sev.prnewswire.com/chemical/20041025/DEM05525102004-1.html, and
http://www.cibasc.com/index/ind-index/ind-automotive/products-9/ind-aut-p-
ro-plastic_additives-2/ind-aut-pro-pla-tinuvin_xt--850.htm.

[0030]As quoted from this public source, Lowilite 36 is a high molecular
weight, benzotriazole UV absorber that offers excellent thermal
properties and is particularly suited to applications requiring low
volatility and high stabilizer loading. It is an excellent choice as
light stabilizer for high temperature polymers like polycarbonate. The
high molecular weight and the resulting low migration combined with good
compatibility in the target polymers make Lowilite 36 helpful in
preventing `plate out` that is caused by additives collecting on parts of
the processing unit.

[0031]As quoted from this public source, Lowilite 234 is a benzotriazole
UV light absorber offering the advantage of particularly low volatility.
This feature makes it especially suitable for applications involving high
temperature processing such as automotive coatings,
polyethyleneterephthalate, polycarbonate, and nylon, where additives may
sometimes be lost due to high temperature levels.

[0032]As quoted from this public source, Lowilite 19 is a monomeric high
molecular weight, sterically hindered amine light stabilizer (HALS) that
is ideally suited to pigmented polyolefin applications due to its low
interaction with the pigments. With a high molecular weight structure, it
is also suitable for applications requiring low volatility and high
migration resistance. Lowilite 19 is also an effective antioxidant and
contributes significantly to the long term heat stability of polyolefins.

[0033]As quoted from this public source, Tinuvin 850 XT is a high
performance light stabilization system for weatherable polyolefins. Its
use is recommended especially for paintable TPO for automotive interior
and exterior applications. It is also highly effective in nonpainted
molded-in-color automotive applications and for nonautomotive
applications. It is a trade secret combination of hindered amine light
stabilizers.

[0034]Optional Additives

[0035]The nanocomposite of the present invention can include conventional
plastics additives in an amount that is sufficient to obtain a desired
processing or performance property for the ultimate thermoplastic
compound, but in a manner that does not disrupt the desired performance
properties.

[0036]The amount should not be wasteful of the additive nor detrimental to
the processing or performance of the compound. Those skilled in the art
of thermoplastics compounding, without undue experimentation but with
reference to such treatises as Plastics Additives Database (2004) from
Plastics Design Library (www.williamandrew.com), can select from many
different types of additives for inclusion into the nanocomposites of the
present invention.

[0038]Of these optional additives, the polyolefin nanocomposite can have
impact modifiers included therein. Impact modifiers are typically
elastomers such as natural rubber, polyisoprene rubber, styrene-butadiene
rubber, polybutadiene rubber, nitrite rubber, butyl rubber,
ethylene-propylene-diene rubber (EPDM), ethylene-propylene,
ethylene-hexene, and ethylene-octene copolymers, and other elastomers.
Minor amounts of impact modifiers can alter the impact strength according
to preferences of those skilled in the art, to be determined without
undue experimentation. For example, polybutadiene rubber,
ethylene-propylene-diene rubber (EPDM), ethylene-octene copolymers, and
other elastomers are useful. Non-limiting examples of such elastomers are
those commercially available from multinational companies such as Bayer,
Dow Chemical, Uniroyal Chemical, ExxonMobil, and others. ENGAGE® 8180,
ENGAGE® 8842, and other ENGAGE® polyolefin elastomers are
especially preferred ethylene-octene copolymers available from Dow
Chemical of Midland, Mich. that function well as impact modifiers for
nanocomposites of the invention.

[0039]Optional Polymers

[0040]While the nanocomposite can be made without other polymers present,
it is optional to introduce other polymers into the extruder for a
variety of ultimate compound properties and performances, but in a manner
that does not disrupt the performance property of the nanocomposite.
These materials can be blended, co-extruded, or otherwise laminated with
the polyolefin for composite structures. Other resins include those
selected from the group consisting of polyolefins, polyimides,
polycarbonates, polyesters, polysulfones, polylactones, polyacetals,
acrylonitrile-butadiene-styrene resins (ABS), polyphenyleneoxide (PPO),
polyphenylene sulfide (PPS), polystyrene, styrene-acrylonitrile resins
(SAN), styrene maleic anhydride resins (SMA), aromatic polyketones (PEEK,
PED, and PEKK) and mixtures thereof.

[0041]Table 1 shows ranges of acceptable, desirable, and preferred weight
percents of the various ingredients for addition to the extruder,
relative to the total weight of the nanocomposite emerging from the
extruder, all being expressed as approximate values. Because the
additives and other polymers are optional, the low end of each range is
zero.

[0043]The preparation of compounds of the present invention is
uncomplicated. The compound of the present can be made in batch or
continuous operations. The compound can start from a concentrate of
organoclay in a thermoplastic (also called a masterbatch) or original
ingredients.

[0044]Mixing occurs in an extruder that is elevated to a temperature that
is sufficient to melt the polyolefin, any optional concentrate
thermoplastic matrix in a concentrate, and any optional other polymers
and to adequate disperse the organoclay and optional additives
therewithin.

[0045]Extruders have a variety of screw configurations, including but not
limited to single and double, and within double, co-rotating and
counter-rotating. Extruders also include kneaders and continuous mixers,
both of which use screw configurations suitable for mixing by those
skilled in the art without undue experimentation. In the present
invention, it is preferred to use a twin co-rotating screw in an extruder
commercially available from Coperion Werner-Pfleiderer GmbH of Stuttgart,
Germany.

[0046]Extruders have a variety of heating zones and other processing
parameters that interact with the elements of the screw(s). Extruders can
have temperatures and other conditions according to acceptable,
desirable, and preferable ranges as shown in Table 2.

[0047]Location of ingredient addition into the extruder can be varied
according the desired duration of dwell time in the extruder for the
particular ingredient. Table 3 shows acceptable, desirable, and
preferable zones when ingredients are to be added in the process of the
present invention.

[0048]Extruder speeds can range from about 50 to about 1200 revolutions
per minute (rpm), and preferably from about 600 to about 1000 rpm,
maximizing output without sacrificing temperature control.

[0049]Typically, the output from the extruder is pelletized for later
extrusion or molding into polymeric articles.

[0050]Subsequent Processing

[0051]The nanocomposite made according to the present invention can serve
either as a concentrate or as a compound. If the former, then the
nanocomposite is an intermediate product, an ingredient to be added with
other ingredients to subsequent compounding steps in a batch or
continuous mixing apparatus. The dilution or "let-down" of the
concentrate into the compound can result in an organoclay concentration
in the compound ranging from about 0.25 to less than 30 weight percent,
and preferably from about 3 to about 12 weight percent.

[0052]Ultimately, the compound is formed into an article using a
subsequent extrusion or molding techniques. These techniques are well
known to those skilled in the art of thermoplastics polymer engineering.
Without undue experimentation but using references such as "Extrusion,
The Definitive Processing Guide and Handbook"; "Handbook of Molded Part
Shrinkage and Warpage"; "Specialized Molding Techniques"; "Rotational
Molding Technology"; and "Handbook of Mold, Tool and Die Repair Welding",
all published by Plastics Design Library (www.williamandrew.com), one can
make films of any laminate structure or articles of any conceivable shape
and appearance using nanocomposites of the present invention.

Usefulness of the Invention

[0053]Nanocomposites of the present invention are useful for making
articles of any shape. Films can be a single layer or multi-layer
laminates. Any of the articles of the present invention can be made to
have a particular color by use of color concentrates from PolyOne
Corporation. Thus, conventional thermoplastic compounds that need
increased stiffness and toughness as provided by organoclay additives can
now have longer heat stabilized properties.

[0054]Further embodiments of the invention are described in the following
Examples

Examples

[0055]A matrix of materials was prepared using a fixed formulation of
organoclay, compatibilizer, polypropylene, and conventional stabilizers
and antioxidants, with varied types of metal scavengers. Table 4 shows a
masterbatch or concentrate used for the examples.

[0059]The samples were then subjected to long term heat aging by placing
the samples in an oven at 150° C. with periodic observation for
visual evidence of localized discoloration or crumbling, crazing, or
pinholes in the samples. Table 8 shows the results.

[0060]Double-digit increase in heat stability is significant because each
increment of accelerated aging time predicts a multiple of actual aging
time in less harsh conditions. With more than 30 days of stability of
long term heat aging under the accelerated conditions, one can predict
years of actual performance life using polyolefin nanocomposites of the
present invention. Therefore, the addition of metal scavengers increases
the effective life of an article made from a polyolefin nanocomposite of
the present invention.

[0061]The invention is not limited to the above embodiments. The claims
follow.